Sector

A sector (or leg) is one complete flight from takeoff at one airport to landing at another. A pilot flying from London to Paris operates one sector; a pilot flying London → Paris → Rome → London operates three sectors.

The number of sectors flown in a day affects crew scheduling and fatigue management:

• Long-haul operations typically involve 1 sector per duty period
• Short-haul and regional operations may involve 4-6 sectors per day
• More sectors mean more takeoffs and landings (the most demanding phases of flight) and more time spent at low altitude in congested airspace
• Fatigue regulations typically reduce maximum duty time as the number of sectors increases

In maintenance, the term flight cycle is equivalent to one sector — each takeoff and landing counts as one cycle. Certain structural components (especially the pressurized fuselage) have life limits expressed in flight cycles because the repeated pressurization and depressurization causes metal fatigue.